1. Field of the Invention
The invention relates to a thin film magnetic head comprising at least an inductive magnetic transducer for writing and a method of manufacturing the same.
2. Description of the Related Art
In recent years, performance improvement in thin film magnetic heads has been sought in accordance with an increase in surface recording density of a hard disk drive. As a thin film magnetic head, a composite thin film magnetic head has been widely used. A composite thin film magnetic head has a layered structure which includes a recording head with an inductive magnetic transducer for writing and a reproducing head with a magnetoresistive device (referred to as MR device in the followings) for reading-out. There are a few types of MR devices: one is an AMR device that utilizes an anisotropic magnetoresistive effect (referred to as AMR effect in the followings) and the other is a GMR device that utilizes a giant magnetoresistive effect (referred to as GMR effect in the followings). A reproducing head using the AMR device is called an AMR head or simply an MR head. A reproducing head using the GMR device is called a GMR head. The AMR head is used as a reproducing head whose surface recording density is more than 1 gigabit per square inch. The GMR head is used as a reproducing head whose surface recording density is more than 3 gigabits per square inch.
The AMR head includes an AMR film having the AMR effect. The GMR head has the similar configuration to the AMR head except that the AMR film is replaced with a GMR film having the GMR effect. However, compared to the AMR film, the GMR film exhibits a greater change in resistance under a specific external magnetic field. Accordingly, the reproducing output of the GMR head becomes about three to five times greater than that of the AMR head.
In order to improve the performance of a reproducing head, the MR film may be changed from an AMR film to a GMR film or the like which is made of a material with more excellent magnetoresistive sensitivity. The pattern width of the MR film, specifically the MR height, may be adjusted appropriate. The MR height is the length (height) between the edge of an MR element closer to an air bearing surface and the other edge, and is determined by an amount of polishing the air bearing surface. The air bearing surface (ABS) is a surface of a thin film magnetic head facing a magnetic recording medium and is also called a track surface.
Performance improvement in a recording head has also been expected in accordance with the performance improvement in a reproducing head. The main factor which determines the performance of a recording head is a throat height (TH). The throat height is a length (height) of a portion of a magnetic pole from the air bearing surface to an edge of an insulating layer which electrically isolates a thin film coil for generating a magnetic flux. It is necessary to reduce the throat height in order to improve the performance of the recording head. The throat height is also controlled by an amount of polishing the air bearing surface.
It is necessary to increase the track density of a magnetic recording medium in order to increase the recording density among the performance of a recording head. In order to achieve this, it is necessary to realize a recording head with a narrow track structure in which the width of a bottom pole and a top pole sandwiching a write gap on the air bearing surface is reduced to the order of some microns to submicron. Semiconductor processing technology is used to achieve the narrow track structure.
Now, an example of a method of manufacturing the composite thin film magnetic head will be described as an example of a method of manufacturing the thin film magnetic head of the related art with reference to FIG. 30 to FIG. 35.
In the manufacturing method, as shown in FIG. 30, an insulating layer 102 about 5 to 10 xcexcm thick made of alumina (aluminum oxide, Al2O3), for example, is deposited on a substrate 101 made of altic (Al2O3 and TiC), for example. Then, a bottom shield layer 103 for a reproducing head is formed on the insulating layer 102. Next, for example, alumina about 100 to 200 nm thick is deposited on the bottom shield layer 103, whereby a shield gap film 104 is formed. Next, an MR film 105 of a few tens of nanometers in thickness for making up the MR element for reproducing is formed on the shield gap film 104, and is patterned to a desired shape by photolithography with high precision. Next, a lead layer (not shown in figure) as a lead electrode layer which is electrically connected to the MR film 105 is formed on both sides of the MR film 105. Then, a shield gap film 106 is formed on the lead layer, the shield gap film 104 and the MR film 105, and the MR film 105 is buried in the shield gap films 104 and 106. Next, a top shield-cum-bottom pole (referred to as a bottom pole in the followings) 107 made of permalloy (NiFe), for example, which is a magnetic material used for both the reproducing head and the recording head, is formed on the shield gap film 106.
Next, as shown in FIG. 31, a write gap layer 108 made of an insulating film such as an alumina film is formed on the bottom pole 107, and a photoresist film 109 is formed in a predetermined pattern on the write gap layer 108 by photolithography with high precision. Then, a first layer of a thin film coil 110 for an inductive recording head made of copper (Cu), for example, is formed on the photoresist film 109 by plating, for example. Next, a photoresist film 111 is formed in a predetermined pattern so as to cover the photoresist film 109 and the coil 110 by photolithography with high precision. A heat treatment at 250xc2x0 C., for example, is applied in order to flatten the photoresist film 111 and to isolate between the turns of the coil 110. Then, a second layer of a thin film coil 112 made of copper, for example, is formed on the photoresist film 111 by plating, for example. Next, a photoresist film 113 is formed in a predetermined pattern on the photoresist film 111 and the coil 112 by photolithography with high precision, and a heat treatment at 250xc2x0 C., for example, is applied in order to flatten the photoresist film 113 and to isolate between the turns of the coil 112.
Next, as shown in FIG. 32, an opening 108a for forming a magnetic path is formed in a rear position (right-hand side in FIG. 32) of the coils 110 and 112 by partially etching the write gap layer 108. Then, a top yoke-cum-top pole (referred to as a top pole in the followings) 114 made of a magnetic material for a recording head such as permalloy is selectively formed on the write gap layer 108, the photoresist films 109, 111 and 113. The top pole 114 is in contact with the bottom pole 107 in the above-mentioned opening 108a and is magnetically coupled to each other. Next, after etching the write gap layer 108 and the bottom pole 107 about 0.5 xcexcm thick by ion milling using the top pole 114 as a mask, an overcoat layer 115 made of alumina, for example, is formed on the top pole 114. A thin film magnetic head is completed after performing machine processing on the slider to form a track surface of a recording head and a reproducing head, that is, an air bearing surface 120.
FIG. 33 to FIG. 35 show a completed structure of a thin film magnetic head. FIG. 33 shows a cross section of the thin film magnetic head vertical to the air bearing surface 120, while FIG. 34 shows an enlarged cross section of the magnetic pole portion parallel to the air bearing surface 120, and FIG. 35 shows a plan view. FIG.32 corresponds to a cross-sectional view taken along the line XXX IIxe2x80x94XXX II of FIG. 35. In FIG. 33 to FIG. 35, the overcoat layer 115 is omitted.
In order to improve the performance of a thin film magnetic head, it is important to precisely form the throat height TH, an apex angle xcex8, a pole width P2W and a pole length P2L shown in FIG. 33 and FIG. 34. The apex angle xcex8 is an angle between a line connecting the corners of the side surfaces of the photoresist films 109, 111, 113 on the track surface side and the upper surface of the top pole 114. The pole width P2W determines a write track width of the recording medium. The pole length P2L represents the thickness of the magnetic pole. In FIG. 33 and FIG. 35, xe2x80x9cTH0 position xe2x80x9d is the position of the edge of the photoresist film 109 on the air bearing surface 120 side, which is an insulating layer for electrically isolating the thin film coils 110 and 112, and represents a reference position when the throat height TH is determined.
As shown in FIG. 34, a structure in which sidewalls of the top pole 114, the write gap layer 108 and part of the bottom pole 107 are vertically formed in a self-aligned manner is called a trim structure. With the trim structure, increase of an effective track width caused by a spread of the magnetic flux occurred while writing on the narrow track can be suppressed. As shown in FIG. 34, a lead layer 121 as a lead electrode layer, which is electrically connected to the MR film 105, is provided on both sides of the MR film 105. The lead layer 121 is omitted in FIG. 30 to FIG. 33.
FIG. 36 shows a plan structure of the top pole 114. As shown in FIG. 36, the top pole 114 comprises a yoke 114a, which makes up most of the top pole 114, and a pole tip 114b with almost a constant width W100 as the pole width P2W. In the connection between the yoke 114a and the pole tip 114b, the outer edge of the yoke 114a forms an angle xcex1 with the surface parallel to the air bearing surface 120, while the outer edge of the pole tip 114b forms an angle xcex2 with the surface parallel to the air bearing surface 120. xcex1 is about 45xc2x0 degrees, for example, and xcex2 is 90xc2x0 degrees. The width of the pole tip 114b determines the write track width of the recording medium. A portion F is the front side of the TH0 position (close to the air bearing surface 120) of the pole tip 114b and a portion R is the rear side of the TH0 position (close to the yoke 114a) of the pole tip 114b. As shown in FIG. 33, the portion F is extended on the flat write gap layer 108, and the portion R and the yoke 114a are extended on a coil portion (called as an apex portion in the followings) which is covered with the photoresist films 109, 111, and 113 and is protruded like a mountain.
The distinctive shape of the top pole is disclosed in Japanese Patent Application laid-open No. Hei 8-249614, for example.
It is necessary to precisely form the pole width P2W in order to determine the write track width of the recording head. Especially in recent years, in order to attain high surface recording density, that is, to form the recording head with a narrow track structure, microfabrication in which the pole width P2W of the top pole is formed equal to or less than 1.0 xcexcm is required.
As a method of forming the top pole, for example, frame plating method is used as disclosed in Japanese Patent Application laid-open No. Hei 7-262519. When the top pole 114 is formed by the frame plating method, first, a thin electrode film made of permalloy, for example, is formed all over the apex area by sputtering, for example. Next, a photoresist film is formed thereon by applying photoresist, and the photoresist film is patterned in a desired shape through photolithography in order to form a photoresist pattern to be a frame for forming a top pole by plating. The top pole 114 is formed by plating with the electrode film formed earlier being a seed layer and the photoresist pattern being a mask.
There is, for example, 7 to 10 xcexcm or more difference in height between the apex area and other areas. On the apex area, a photoresist of 3 to 4 xcexcm thick is applied. If the film thickness of the photoresist formed on the apex area is required to be 3 xcexcm or more, a photoresist film about 8 to 10 xcexcm thick or more, for example, is formed in the lower part of the apex area since the photoresist with liquidity gathers into a lower area.
In order to form the narrow track as described, it is necessary to form a frame pattern with a width of about 1.0 xcexcm using a photoresist film. That is, a micro pattern with a width of 1.0 xcexcm or less is to be formed by the photoresist film of 8 to 10 xcexcm or thicker. However, it is extremely difficult in a manufacturing process to form such a thick photoresist pattern with a narrow pattern width.
In addition, during an exposure of photolithography, a light for the exposure reflects by an undercoat electrode film as a seed layer and the photoresist film is exposed also by the reflecting light causing deformation of the photoresist pattern and the like. As a result, a photoresist pattern with a sharp and precise pattern shape can not be attained. Therefore, the side walls of the top pole take a round shape so that the top pole can not be formed in a desired shape. Especially, as shown in FIG. 37, it is further difficult to attain a desired width W100A by further microfabricating the pole width P2W. It is because the reflecting light reflected by the undercoat electrode film in the area R of the pole chip portion 114b extended on the apex area includes not only the reflecting light in a vertical direction but also the reflecting light from the slope of the apex area in an oblique direction or in a lateral direction influencing the exposure of the photoresist film. As a result, the pattern width of the photoresist pattern which determines the pole width P2W becomes greater than the anticipated value (as shown by the broken line) and it takes a shape as shown by a solid line in FIG. 37. The width of the portion F of the pole tip 114b which is front of TH0 position (air bearing surface 120 side) is an extremely important factor for determining the track width on the recording medium. Therefore, if the width of the portion F becomes greater than the above-mentioned value W100A, the targeted minute track width can not be attained.
Such problems also exist in the above-mentioned magnetic head disclosed in Japanese Patent laid-open No. Hei 8-249614. It is because, in this magnetic head, the width of the portion which is front of the TH0 position (air bearing surface 120 side) can not be precisely controlled because of the influence on the exposure of the photoresist film by a reflecting light from the apex area in an oblique direction and a lateral direction since the pole width moderately changes from the TH0 position towards the yoke.
As shown in FIG. 37, the portion R of the pole tip 114b, which extends from the TH0 position to the connection between the pole tip 114b and the yoke 114a, has about the same width as the portion F which extends from the TH0 position to the air bearing surface 120, and the portion R has a smaller cross-sectional area. As a result, the magnetic flux from the yoke 114a is saturated in the portion R and can not sufficiently reach the portion F which determines the track width. Therefore, the overwrite performance, that is, the characteristic of overwriting data on a recording medium on which data has already been written, is reduced to a degree about 10 to 20 dB, for example, so that a sufficient overwrite performance can not be attained.
The invention has been designed to overcome the foregoing problems. The object is to provide a thin film magnetic head in which precise control of the pole width can be performed and a sufficient overwrite performance can be attained even in a case where the pole width is microfabricated, and a method of manufacturing such a thin film magnetic head.
A thin film magnetic head comprises: two magnetic layers magnetically coupled to each other having two magnetic poles which face each other with a gap layer in between and are to be faced with a recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers; wherein one of the two magnetic layers includes: a first magnetic layer portion extending from recording-medium-facing surface in a longitudinal direction to be away from the recording-medium-facing surface, and having a constant width for defining a write track width of a recording medium; and a second magnetic layer portion magnetically coupled to the first magnetic layer portion in the rear edge of the first magnetic layer portion on the side away from the recording-medium-facing surface; wherein a coupling position at which the first and second magnetic layer portions are coupled each other is closer to the recording-medium-facing surface than the front edge of the insulating layer on the side close to the recording-medium-facing-surface; and at least the portion of the second magnetic layer portion between the front edge of the insulating layer and the rear edge of the first magnetic layer portion has a width wider than that of the first magnetic layer portion.
A method of manufacturing a thin film magnetic head of first aspect of the invention is a method of manufacturing a thin film magnetic head including two magnetic layers magnetically coupled to each other having two magnetic poles which face each other with a gap layer in between and are to be faced with a recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers; formation of one of the two magnetic layers is performed by the steps of: forming a first magnetic layer portion extending from recording-medium-facing surface in a longitudinal direction to be away from the recording-medium-facing surface, and having a constant width for defining a write track width of a recording medium; and forming a second magnetic layer portion magnetically coupled to the first magnetic layer portion in the rear edge of the first magnetic layer portion on the side away from the recording-medium-facing surface; wherein a coupling position at which the first and second magnetic layer portion are coupled each other is closer to the recording-medium-facing surface than a front edge of the insulating layer on the side close to the recording-medium-facing-surface; and at least the portion of the second magnetic layer portion between the front edge of the insulating layer and the rear edge of the first magnetic layer portion has a width wider than that of the first magnetic layer portion.
In the thin film magnetic head of the invention or the manufacturing method of a thin film magnetic head of the one aspect of the invention, the write track width of a recording medium is defined by the constant width of a first magnetic layer portion. The first magnetic layer portion is magnetically coupled to a second magnetic layer portion in the rear edge further from the recording medium. The coupling position between the first magnetic layer portion and the second magnetic layer portion is located on the side closer to the recording-medium facing surface than the front edge of the insulating layer which is close to the recording-medium facing surface, and at least the portion of the second magnetic layer portion between the front edge of the insulating layer and the rear edge of the first magnetic layer portion has a width wider than that of the first magnetic layer portion. Therefore, enough magnetic volume is maintained in this area.
In a thin film magnetic head of the invention or a manufacturing method of a thin film magnetic head of the one aspect of the invention, a step in a width direction may be formed at the coupling position of the first magnetic layer portion and the second magnetic layer portion. In such a case, a step face vertical to an extending direction of the first magnetic layer portion may be formed at the coupling position. Further in a case of a thin film magnetic head comprising a magnetic transducer film extending from the recording-medium-facing surface in a longitudinal direction to be away from the recording-medium-facing surface, preferably the coupling position may be located between the rear edge of the magnetic transducer film and the front edge of the insulating layer. In the case, the length from the recording-medium-facing surface to the front edge of the insulating layer may preferably lie within the range of one-and-a-half to six times the length of the magnetic transducer film.
In a thin film magnetic head of the invention or a manufacturing method of a thin film magnetic head of the one aspect of the invention, the one of the two magnetic layers may further include a third magnetic layer portion which is magnetically coupled to the second magnetic layer portion and extends to cover a part of the thin film coil with the insulating layer in between. In such a case, the first, second and third magnetic layer portions may be integrally formed in one piece through a series of the manufacturing steps. Otherwise, the first and second magnetic layer portions may be integrally formed in one piece through a series of the manufacturing steps and the third magnetic layer portion may be formed separately from the first and second magnetic layer portions through a manufacturing step different from the steps of manufacturing the first and second magnetic layer portions. In this case, the third magnetic layer may be preferably formed so that the third magnetic layer extends overlapping at least a part of the second magnetic layer portion.
In a thin film magnetic head of the invention or a manufacturing method of a thin film magnetic head of the one aspect of the invention, the gap layer may have a region with a flat surface, the thin film coil may be formed on the flat region of the gap layer; and the insulating layer may include an insulating film which covers the whole of the thin film coil and a part of the gap layer. In such a case, the position of the front edge of the insulating layer may be preferably defined by an edge of the insulating film on the side closer to the recording-medium-facing surface. Also, the first magnetic layer portion may be preferably located on a part of the region with a flat surface of the gap layer, the part of the region being not covered with the insulating film. In this case, the second magnetic layer portion may preferably extend from the coupling position onto the slope of the insulating film. In this case, the second magnetic layer portion may terminate on the slope of the insulating film; and the insulating layer may preferably include another insulating film formed to fill a space over the insulating film up to the same level as a top surface of the second magnetic layer portion.
In a thin film magnetic head of the invention or a manufacturing method of a thin film magnetic head of the one aspect of the invention, the other magnetic layer of the two magnetic layers may include a fourth magnetic layer portion with a flat surface, and a fifth magnetic layer portion located facing the first and second magnetic layer portions with the gap layer in between and magnetically coupled to the fourth magnetic layer portion; and the thin film coil may be buried between the fourth magnetic layer portion and the gap layer with a part of the insulating layer in between. In this case, the position of the front edge of the insulating layer may preferably be defined by the rear edge of the fifth magnetic layer portion, the rear edge being on the side closer to the recording-medium-facing surface. Also, when the gap layer may have a region with a flat surface; the insulating layer may include an insulating film formed on the opposite side of the thin film coil with the gap layer in between, the first magnetic layer portion may be located on a part of the region with a flat surface of the gap layer, the part of the region being not covered with the insulating film and the second magnetic layer portion may extend from the coupling position onto the slope of the insulating film.
A method of manufacturing a thin film magnetic head in another aspect of the invention is a method of manufacturing a thin film magnetic head including two magnetic layers magnetically coupled to each other having two magnetic poles which face each other with a gap layer in between and are to be faced with a recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers; wherein one of the two magnetic layers includes: a first magnetic layer portion extending from recording-medium-facing surface in a longitudinal direction to be away from the recording-medium-facing surface, and having a constant width for defining a write track width of a recording medium; and a second magnetic layer portion magnetically coupled to the first magnetic layer portion in the rear edge of the first magnetic layer portion on the side away from the recording-medium-facing surface; the method comprising: a step of forming an insulating film on the gap layer with a flat surface, the insulating film having a slope towards the surface of the gap layer and constituting at least a part of the insulating layer; a step of forming a photoresist layer so as to cover the gap layer and the insulating film; a first exposure step of selectively exposing a first region of the photoresist layer including a region corresponding to the first magnetic layer portion, the first region corresponding to a flat region of the gap layer; and a second exposure step of selectively exposing at least a second region of the photoresist layer corresponding to the second magnetic layer portion, the second region corresponding to a region from the slope of the insulating film to the flat region of the gap layer: wherein the first region and the second region partially overlap each other.
In a method of manufacturing a thin film magnetic head of another aspect of the invention, after the insulating film, which constitutes at least a part of the insulating layer, is formed on the flat gap layer, a photoresist layer is formed so as to cover the gap layer and the insulating layer. Then, the first region of the photoresist layer in the flat region of the gap layer, the first region including a region corresponding to the first magnetic layer portion, is selectively exposed. Also, at least the second region of the photoresist layer from the slope of the insulating film to the flat region of the gap layer, the second region corresponding to the second magnetic layer portion, is selectively exposed so as to partially overlap the first region.
In a method of manufacturing a thin film magnetic head in another aspect of the invention, the second magnetic layer portion may preferably be formed so that: a coupling position at which the first magnetic layer portion and the second magnetic layer portion are coupled each other is closer to the recording-medium-facing surface than the front edge of the insulating layer on the side close to the recording-medium-facing-surface; and at least the portion of the second magnetic layer portion between the front edge of the insulating layer and the rear edge of the first magnetic layer portion has a width wider than that of the first magnetic layer portion.
A method of manufacturing a thin film magnetic head in another aspect of the invention, the first region may include:a constant-width part having a constant width, which extends from the recording-medium-facing surface in a longitudinal direction to be away from the recording-medium-facing surface and defines the write track width of the recording medium; and a wide-width part with a width wider than the constant-width part, at least a part of the wide-width part overlapping the second region. Also, the first region may have a substantially constant width at any point in a longitudinal direction.
In a method of manufacturing a thin film magnetic head in another aspect of the invention, the one of the magnetic layer further may include a third magnetic layer which is magnetically coupled to the second magnetic layer portion and extends to cover a part of the thin film coil with the insulating layer in between, and a third region of the photoresist layer corresponding to the third magnetic layer portion simultaneously may be exposed by the second exposure step. In such a case, preferably it may include a development step of forming a first photoresist pattern by developing the first and second regions which have been exposed, all together; and a step of integrally forming the first, second and third magnetic layer portion in one piece using the first photoresist pattern. Also, when the one of the two magnetic layers further includes a third magnetic layer portion which is magnetically coupled to the second magnetic layer portion and extends to cover a part of the thin film coil with the insulating layer in between; the method further preferably may include: a third exposure step of exposing a third region corresponding to the third magnetic layer; a development step of forming a third photoresist pattern by developing the third region exposed in the third exposure step; and a step of forming the third magnetic layer portion using the third photoresist pattern.
Other and further objects, features and advantages of the invention will appear more fully from the following description.